This invention relates to an end construction for forming a pinch closure for the opening in an end of a multi-ply, tubular bag, such as the outer, protective shell of a dunnage bag. This invention is particularly concerned with an end construction which can be expeditiously converted into a strong and durable, pinch closure, without the need for repetitive, manual steps.
Pinch closures for the ends of multi-ply, tubular bags are well known in the art. See, for example, the pinch closure for the outer shell of a dunnage bag in U.S. Pat. No. 3,365,116.
Such pinch closures have been formed from an end construction which includes an angle-cut flap on one side of each ply of the bag and an angle-cut cut-out in the other side of each ply of the bag. Each flap has been adapted to fold over the opening in the end of the multi-ply, tubular bag and to be interleaved between and adhesively bonded to the portions of the plies on the other side of the opening in the bag. In forming the pinch closure, each flap has been folded about a fold line, coincidental with the opening in the end of the bag, surface coated with an adhesive, and then manually interleaved between the portions of the plies on the other side of the opening in the end of the bag. A strong, pinch closure for a multi-ply bag has been formed in this way. In fact, in dunnage bags, the resulting pinch closure for the outer protective shell has been found to be sufficiently strong so that the closure does not break when the bladder, inside the multi-ply shell, is inflated or the dunnage bag is squeezed between shifting loads of freight in a freight car.
However, such end constructions in multi-ply bags have been somewhat unsatisfactory due to the need for manually interleaving several flaps between plies to form the pinch closure. That manual interleaving of the plies has been required has been considered as unduly increasing the cost of producing such multi-ply bags. There has been an unfilled need, therefore, for a means of forming a pinch closure in a multi-ply bag without the need for manually interleaving flaps to close the opening in the end of the bag and without sacrificing the strength or durability of the bag.